Abstract
I AM in the habit of saying, “the amount of momentum is 12 in C.G.S. units” or the amount of momentum is 12 in engineers' units. The use of such a complex name as gram-centimetre per second would be absurd. Now Mr. Barrell has made an excellent suggestion; the names sec-dyne with all students, and sec-pound with such students as use engineers' units, are not only short and easy to remember, but they keep before the student the fundamental fact that force is time rate of change of momentum. It seems to me, however, that at the start we must define, momentum as m, and boys must from the start learn that they are no longer multiplying mere numbers. I never found that a boy had any difficulty if his master did not create one. A boy knows at once that if a distance of 100 yards is passed over in, 20 seconds there is an average speed of 5 yards per second; he has no difficulty in dividing space by time, but his teacher may create great confusion in his mind if he philosophises about it.
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PERRY, J. The Unit of Momentum. Nature 88, 144 (1911). https://doi.org/10.1038/088144b0
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DOI: https://doi.org/10.1038/088144b0
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